Process for manufacturing piston rings



Dec. 12, 1939. w. J. SIX

PROCESS FOR MANUFACTURING PISTON RINGS Filed June 10, 19:57 s'sheets-sheet 1 Dec. 12, 1939.

PROCESS FOR MANUFACTURING PISTON RINGS W. J. SIX

Filed June 10, 1957 5 Sheets-Sheet 2 Dec. 12, 1939. w. J. SIX 2, 3, 5

PROCESS FOR MANUFACTURING PISTON RINGS Filed June 10, 1937 5 Sheets-Sheet 3 Dec. 12, 1939. w. J. SIX

PROCESS FOR MANUFACTURING PISTON RINGS Filed June 10, 1937 5 Sheets-Sheet 4 Dec. 12, 1939. w. J. SIX

PRQCESS FOR MANUFACTURING PISTON RINGS Filed June 10, 1937 5 Sheets-Sheet 5 to bend into rings.

of a different magnitude.

Patented Dec. 12, 1939 UNITED STATES PATENT OFFICE Walter J. Six, Indianapolis, Ind. Application June 10, 1937, Serial No. 147,397

15 Claims.

their efficiency, particularly when used in modern automobile engines, in which the conditions of wear are very much aggravated and more exacting performance is demanded, due to the high rate of speed and reciprocation of the pistons and the high pressures and temperatures developed in the engine cylinders.

It has also been proposed heretofore to make piston rings of steel wire, the wire being formed into the rings in different ways and subjected to various heat treating operations. Steel wire. when first hardened so as to withstand wear and abrasion, has been found difilcult or impractical When the steel wire has been sufficiently soft to permit readily forming of the rings, the rings have not been durable and they lost their shape and tension easily. Should the soft steel rings be hardened by heating and cooling, as has been proposed, the rings become distorted during the quenching operation and it is also difilcult, if not impractical, to machine them. I am aware that it has been suggested that piston rings first be formed to the desired shape and then be confined in restraining dies and quenched in oil. Such operations, as have been suggested, however, fail to produce a satisfactory ring because metals, such as steel, upon being quenchhardened first undergo a severe volume contraction immediately followed by a volume expansion The restraining dies cannot accommodate or follow these volume changes of the metal or confine the metal to the accurate shape required. Even subsequent corrective heat treating and machining operations, which would of themselves add materially to the costs, do not serve to overcome the difficulties heretofore encountered.

The principal object of my invention is to provide a novel process which is more simple and effective than the prior practices in producing piston rings or the like, and which overcomes faults and deficiencies existing in prior rings. One of the principal features or steps of my invention is to heat treat the ring and permanently impart to the ring its desired ultimate shape or form during the quenching operation and as the metal transforms from its austenitic state to its martensitic state. More particularly, I form the ring to the desired curvature or contour by means of suitable forming means after the physical volume changes have substantially taken place but while the metal is still in a semi-plastic condition. My invention also comprehends the process comprising other steps in conjunction with such forming step.

The above and other objects of my invention will be apparent from the following description taken in connection with the accompanying drawings in which I have illustrated somewhat generally two forms of apparatus for forming piston rings to the desired shape at the proper time during the quenching operation in accordance with my novel process.

Fig. l is a'perspective view of a group of separate split rings carried by a device or fixture, the rings being heated while on the fixture, which also aligns the rings and readily enables the operator to place the rings in the forming mechanism.

Fig. 2 is a perspective view of those parts of the forming mechanism which clamp the rings against a formed arbor.

Fig. 3 is a longitudinal vertical sectional View 1 taken on the axis of the clamping members and showing an arbor in withdrawn position.

Fig. 4 is a sectional view like that of Fig. 3, except that the rings are shown in section and the arbor is shown in advanced or forming position.

Fig. 5 is a cross-sectional view through the quenching tank and shows the mechanism of Fig. 2 in end elevation.

Fig, 6 is a similar end elevation showing the mechanism of Fig. 1 in closed position and the arbor in section.

Fig. 7 is a perspective view of the formed arbor.

Fig. 8 is a perspective view of a bracket.

Fig. 9 is a perspective view of the flexible sleeve for confining the rings circumferentially against the formed arbor.

Fig. 10 is a perspective View of the piston rings and the means for firmly clamping the formed rings against movement when they are removed from the forming mechanism.

Figs. 11 to 14 show modified forms of devices for performing my process, Fig, 11 being a perspective view of a modified form of forming die adapted for use with or without a formed arbor; Fig. 12 a perspective view of the arbor and guide key adapted tobe mounted on the formed arbor; Fig. 13 a longitudinal section taken through the forming die associated with the formed arbor; Fig. 14 a side view of the piston rings and the means for clamping the rings against movement when they are removed from the forming die.

When manufacturing piston rings formed of steel by my process, I may form the ring by coiling a steel wire of desired cross-section into the form of a closed helix and then separate the turns of wires and form the gaps in the individual circular ring by a saw moved longitudinally to the axis of the helix, as is generally understood in the art. The rings may, however, be formed individually by bending lengths of wire into circular form or by cutting off from a strip each turn as it is formed.

In processing individual split rings in either steel or cast iron, the desired number of rings ll (Fig. 1) are then preferably mounted on the aligning and handling device or fixture l2. This fixture has two grooves or channels i3 and I3 into which the opposed ends of the rings extend. The end surfaces of the rings may lightly engage the bottoms-of the groove without expanding the rings. The fixture has a flange M by which it may be conveniently gripped by some suitable pincers or pliers by the workman as shown.

The rings, mounted on the fixture, are then placed in a suitable furnace or heating device (not shown) in which the heat is carried sufiiciently high until the metal is in a complete austenitic state in which the carbides are in complete solution. The metal selected has a thermal critical temperature which is comparatively high. For example, with steel such as known as S. A. E. 52,100, I find that the rings may be heated at a temperature of from 1700 to 1800 F. for approximately ten to thirty minutes. With respect to cast iron rings, they may be heated to a temperature of from 1600 F. to 1700 F. for approximately ten to twenty minutes.

After this heating operation the rings are withdrawn from the furnace and rapidly cooled or quenched. At the proper time and during the quenching operation the rings are given their desired shape or form by means of forming mechanism disclosed in the drawings and now to be described. In referring to the desired or ultimate shape, form or contour of the piston rings, I mean, of course, the required shape of the finished ring when in its normal or unrestrained state. The piston ring is somewhat elliptical normally but becomes circular when contracted in the engine cylinder.

The forming mechanism is mounted in a tank l6 which may be filled with the quenching liquid such as oil. The mechanism may be constantly immersed in the oil, or. if desired, the oil level may be raised to submerge the forming mechanism at the desired time after the heated rings are put in place preparatory to the quenching and forming operations.

Referring to Figs. 2, 3 and 5, mounted crosswise in the tank there is a U-shaped frame l8. Within the frame are two half-cylindrical clamping members l9 and I9. A hinge or pivot pin 20 projects through overlapping ears 2| and 2i (Fig. 3) on the members l9 and l9 and also through a raised portion 22 at the center of the frame l8.

Fig. 9 shows in perspective a flexible forming sleeve 24 which is shown in place within the clamping member l9 and Iii in Figs. 2, 5 and 6 in particular. The sleeve 24 has radially extending flanges 25 engaging the upper facing edges of the clamping members to which the sleeve is attached ,by means of screws or otherwise.

Each clamping member l9 and 19 is operated through its respective toggle comprising links 21 and 28, the inner end of the link 2 bei g p voted to the upper end of the clamping member, the

outer end of the link 28 being pivoted to the frame l8 and the adjacent ends of the links being pivoted together by a pintle 28. Suspended from each pintle is a yoke 30. Vertical rods 3i which are connected at their upper ends to the respective yokes 3|], project through suitable packing in the bottom of the tank. These rods may be operated by any suitable mechanism, such for example, as by a pneumatically operated piston and proper control devices. Such mechanism and control devices are not shown in'the drawings, and it will suffice to say here that the toggles are so operated as to close and open the clamping members at the desired times as will be pointed out more specifically later.

A bracket 34, shown in perspective in Fig. 8, is fixedly mounted within the tank It as shown in Figs. 3 and 4. The bracket 34 is provided with the circular seat 35 in which a cup shaped clamping member 36 (Figs. 3, 4 and 10) is adapted to be supported. The cup shaped member 38 has a central opening 31 and a slot 38 which, when the member is in position on the bracket 84, are in alignment with a slot 40 through the bracket.

The formed arbor 44 is shown in perspective view in Fig. '7. It is shown in side elevation and retracted position in Fig. 3, and in side elevation and advanced or forming position in Fig. 4. The arbor is form turned or otherwise shaped to the desired inner curvature or contour of the finished piston rings, which is somewhat elliptical. Its advancing end is tapered to facilitate movement of the arbor into the rings. The arbor may be operated, that is, advanced and retracted, by any desired means (not shown), though I prefer to employ a pneumatic or hydraulic motor of the reciprocating piston type.

In carrying out one method of the quenching and forming operations of my process, the operator by means of a suitable tool, such as shown in Fig. 1, places the heated rings, as aligned on the handling fixture l2, within the open flexible forming sleeve 24 with the vertical flange H of the fixture between the upper ends of the sleeve. In this position the side of the right hand ring of the group engages the edge of the cup member 36.

If the forming mechanism is constantly immersed in oil the rapid quenching operation begins as the rings are placed into the tank. If desired, however, it is not necessary to have the forming mechanism constantly submerged, in which event the rings are first placed in the forming sleeve, which is open and out of contact therewith and which may be above the normal oil level and then the level of the oil may be raised, in any desired way, such as by a movable partition in the tank. For convenience I have indicated a normal oil level at 43 in Fig. 3 and the raised oil level at 45 in Fig. 4.

After the rings are placed in the forming sleeve and the oil raised, the toggles 21-28 are partially operated or straightened to move the clamping members l9 and Ill from the fully opened position shown in full lines in Fig. 5 to the intermediate position indicated by dotted lines l9 in such figure. Then the arbor is'advanced from the position shown in Fig. 3 to the position shown in Fig. 4. As the advancing end of the arbor enters the rings, it, or a projection which may be provided on it, strikes the end of the handling fixture l2 and slides the latter out from between 'the ends of the rings, the slot 38 in the holding cup 38 and the slot 40 in the bracket 34 permitting this movement of the fixture.

The rings, as positioned on the fixture, are substantially round or circular and may be of slightly smaller diameter than that of the formed arbor so that as the arbor is forced through the rings it expands them. When the arbor is in its fully advanced position as shown in Fig. 4, the circular shoulder 41, provided on its left hand end, engages the side of the left hand ring of the group so that the rings are firmly compressed or] held against each other axially between the edge of the holding cup 36 and the shoulder 41. At the same time that the arbor is fully advanced to its forming position, the toggles 21-28 are further operated to the position shown in Fig. 6 to close the forming sleeve 24 sothat the latter firmly engages against the outer peripheryof the rings and presses the rings tightly against the formed arbor throughout their length, thereby imparting the desired shape to the rings. In other words, the rings are bent to conform to the exact form of the arbor and are then held firmly confined edgewise, internally and externally.

The rings are formed at a definite period after the quenching operation has started. The arbor is not advanced completely and the iorming sleeve is not clamped tightly against the rings, until the temperature of the metal has i'allen below the critical temperature but these operastrained rings may be subjected to the quench for approximately fifteen seconds with respect to steel rings and five seconds with respect to cast iron rings before they are formed to shape while still in their semi-plastic condition, The quenching operation is continued with the rings in fully confined condition until the metallurgical transformation is complete, and all the soft austenite is metamorphosed into hard martensite, whereupon the rings have become permanently set or fixed to the shape of the arbor.

' With the resilient forming sleeve still in closed clamping position the arbor is withdrawn. Then a bolt 49 (Fig. 10) is inserted through the opening 31in the cup-shaped member 36. The bolt 'has a head which engages the back'of the cup.

Next, a disk 50 is slipped over the threaded end portion of the bolt. a U-shaped washer 5! is mounted on the threaded portion and a nut 52 is tightened so as to clamp the rings firmly in axial alignment between the cup member 36 and the washer 50. The toggles 27-48 are then broken to open the forming sleeve 24 and the rings, as clamped together by the bolt, are re-' moved from the forming mechanism.

The rings now have a hard martensitic structure which is somewhat brittle and too hard for convenient machining or grinding operations which may break them. Accordingly, the rings, as clamped together, are subjected to a drawtempering operation by heatingthe rings, to a temperature below the critical and then cooling the rings. The rings may beheated in the furnace to a temperature of around 800 for about thirty minutes after which they may be rapidly cooled by quenching or permitted to cool in the atmosphere in the case of steel rings. Approximately the same temperature and time interval apply in the case of cast iron rings. The restrained rings, as tempered, still have a substantially martensitic structure, but the hardness of the metal is reduced so that it may be readily machined or ground. The tempering operation does not disturb the shape of or distort the rings, though it does improve the toughness of the metal and increases the tension of the ring. The substantially martensitic structure of the ring resists the high engine temperatures to which it is subjected in use. The ring is highly wearresistant and free from abrasion.

During the courseoi the manufacture of the piston rings various mechanical operations may be performed upon them. For convenience these operations may be generally referred to as me.- chining operations, After the helix is first formed and the longitudinal cut made to separate the rings or turns, I prefer to partially close the rings and perform another cutting operation in order to properly size the joint or gap. For example, in respect to steel rings, after this, operation I may normalize the stresses and strains in the metal by heating the rings to a temperature of possibly around 500 F.- This heat treatment does not change the metallurgical structure of the metal, though it does make the metal somewhat stiffer so that the rings may now be readily rough-ground on their edges. After the rings have been quenched and formed -by the mechanism described above, I prefer to finish grind the edges and finish grind the outside diameters or peripheries of the rings. Referring now to Figs. 11 to 14 (Sheet 5) which show modified mechanisms. it will be seen that for convenience I have used the same reference numerals to designate parts which correspond to the parts shown in ,the other figures and described above.

In Fig. 11 the clamping members l9 and Iii in place of carrying a flexible forming sleeve as described above, support a die comprising three sections 56, 56 and 56 The sections 56 and 56 are rigidly secured to the inner faces of the clamping members l9 and Ill and the bottom section 56 rests loosely upon these clamping members and is prevented from sliding axially of the members by suitable means, such as pins (not shown) which may project from the bottom side of the section into openings in either of the clamping members.

The arbor 44 (Fig. 12) may be provided with a key 58 having aprojection 59 adapted to seat in a recess 60 formed in the taperedend of the arbor. As the arbor is advanced into the piston rings, the forward end of the key strikes the left'hand end of the handling fixture l2 and slides the latter out between the ends of the rings. The key 58 may then be removed, though this may not be necessary as the key may be narrower than the gaps in the piston rings so that but one end of each ring could engage the key during the forming of the rings. A collar 62 is loosely mounted on the arbor so that when the arbor is fully advanced to the position shown in Fig. 13, the piston rings are clamped endwise between the collar and the edge of the cup shaped member 36.

After, or at the time the arbor is fully advanced, the clamping members are moved to their closed position by the toggles 21-48, though the upper ends of the clamping members are not necessarily brought into contact, this preferably being prevented by a stud 64, (Fig. 11) on one of the clamping members. As the clamping members are closed, the bottom die section 56 is in the arbor.

slightly raised and it and the side sections 66 and 56 are-brought into contact with the piston rings so as to clamp the rings against the arbor 44 to form the piston rings to the desired shape. It will be understood that the die sections have their inner faces formed so that when the clamping members are closed they conform to the desired contour of the piston rings, the arbor 44 being likewise formed to shape.

Referring to Fig. 11, slidably mounted between each clamping member and its secured die section is a latch bar 65 having a projecting lip 66. The right hand bar 65 is shown in dotted lines, in order better to show the longitudinal grooves out into the clamping members and side die sections to accommodate the bar. After, or at the time the arbor is moved to its fully advanced position, shown in Fig. 13, the clamping members are closed whereupon the lips 66 of the slidable latch bars 65 move over the left hand end of the collar 62, there being recesses 66 (Fig. 12) in the fiange 41 on the arbor to permit this movement of the ends of the bars 65. The bars 65 are now slid toward the right by suitable mechanism (not shown) in order to hold the collar 62 in fixed position when the arbor is withdrawn toward the left after the piston rings have been formed. Thus the rings remain firmly clamped edgewise between the collar 62 and the cup shaped member 36.

Mounted in the end or base of the cup shaped member 36 is a shouldered collar Ill in which a rod H is slidably mounted. A coiled spring 12, which encircles the rod, is compressed between the collar 10 and a washer 13 which is held on the right hand end of the rod by a nut 14. The other end of the rod has a head 15. It will be seen that when the arbor is in its advanced position the rod projects through a central opening After the arbor is removed from the rod and while the piston rings are clamped edgewise by the latch bars 65, a U-shaped member ll (Fig. 14), similar to the U-shaped member i shown in Fig. 10, is slipped over the left hand end of the rod H and the spring 12 then moves the rod toward the right so that the rings remain clamped between the collar 62 and the cup 36 when the latch bars 65 are released and the clamping jaws l9 and i9 are fully opened. I have not shown in the drawings the means for controlling the operation of the rod H but any desired mechanism may be employed. For example, the rods may be held toward the left by a suitable device at the right hand end of the rod, the device being moved to permit operation of the compressed spring 12 after the washer IT has been placed in position.

The rings, so clamped in edgewise condition, are removed from the forming mechanism and treated further as fully described above.

I have particularly referred to the manufacture of steel rings by my process and have pointed out that my invention is equally applicable to the manufacture of cast iron rings. Such rings may be cast circular in a mold either singly or in multiple, or in an elongated cylindrical ring structure and then carried through substantially the same operations that I have already described. In some instances the rings may be formed by my process before being split, or before a cylindrical blank is divided into the individual rings. Such cylindrical blank may be peripherally cut to define the rings which are held together integrally by a thin film of metal during the forming process. The term ring blank" as used in the appended claims, comprehends such cylindrical blanks as well as individual ring blanks. In forming such ring structures, it may be unnecessary to employ the formed arbor with the rigid sectional clamping or forming die shown in Figs. 11 to 14.

While I have shown and described two forms of mechanisms which may be utilized in carrying out my process, yet it will be understood that various changes may be made in the mechanism and, in fact, various other forms of mechanism may be employed. Nor do I wish to limit my invention to the particular order or number of steps which I have described. The temperatures to which the rings are subjected may be varied dependent partly upon the composition of the metal. I would also point out that air or other mediums than 011 may be employed rapidly to quench the rings.

I claim:

1. The process of manufacturing ferrous metal piston rings which comprises heating the rings above the critical temperature, partially quenchhardening .the rings and then expanding the rings and changing their shape to the desired permanent form below the critical temperature and before the quenching is completed.

2. The process of manufacturing ferrous metal piston rings which comprises heating the rings above the critical temperature, partially cooling the rings in unrestrained condition, and then restraining the rings edgewise and deforming the rings circumferentially to their desired form below the critical temperature and before the cooling is completed.

3. The process of manufacturing split ferrous metal piston rings which comprises heating the split rings above the critical temperature, partially cooling the rings, and then expanding the rings and deforming the rings circumferentially to their desired form below the critical temperature and before the cooling is completed.

4. The process of manufacturing split ferrous metal piston rings which comprises heating the,

split rings above the critical temperature, partially cooling the rings, and then expanding the rings, restraining the rings edgewise and deforming the rings circumferentially to their desired form below the critical temperature and before the cooling is completed.

5. The process of manufacturing ferrous metal piston rings which comprises heating the rings above the critical temperature, partially quenchhardening the rings and then before the metallurgical structure of the metal becomes fixed, restraining the rings edgewise and clamping the rings circumferentially to deform them to the desired shape below the critical temperature.

6. The process of manufacturing ferrous metal piston rings which comprises heating the rings above the critical temperature, partially quenchhardening the rings, and then expanding the rings by exerting pressure around their inner peripheries and deforming the rings by circumferentially exerting pressure against their outer peripheries below the critical temperature and hardening the rings, then expanding the rings by A forcing a formed arbor into the same, restraining the rings edgewise and deforming the rings by clamping the rings against.the arbor below the critical temperature and prior to complete cooling.

8. The process of manufacturing ferrous metal piston rings, comprising heating the rings above the critical temperature, and then changing the shape of the rings to their desired form I below the critical temperature but during the metal piston rings, comprising heating the rings above the critical temperature, quench-hardening the rings to their martensitic state, changing the shape of the rings to their desired form during the quenching operation and while the metal is still sufficiently plastic and approximately at I the time the physical-volume changes, due to the transformation from austenite to martensite, are completed, and subsequently heat treating the rings to a temperature below the critical to reduce the hardness of the metal while retaining a substantial martensite structure.

11. The process of manufacturing resilientferrous metal piston rings, comprising heating the ring blank to the austenitic state,'quenching the heated ring blanks to the martensitic state, and clamping the ring blanks circumferentially after it is partially quenched but during the transition of the metal from-austenite to martensite to change the shape of the ring blank to the desired form.

12. The process of manufacturing ferrous metal piston rings comprising heating the rings to their austenitic state, quenching the rings to their martensiticstate, exerting radial forces on the rings to permanently change the shape of the rings to the desired form during the transition of the metal from austenite to martensite, and restraining the rings axially to prevent distortion during such forming.

13. The process of manufacturing ferrous metal piston rings comprising heating the rings to their austenitic state, quenching the rings to their martensitic state, expanding the rings by inserting a formed arbor therein, clamping the rings against the arbor after the rings are partially quenched but while the metal is still sufficiently plastic to permanently deform the rings to the desired shape, and restraining the rings axially during such deforming.

14. The process of manufacturing resilient ferrous metal piston rings comprising heating split ring blanks above the critical temperature, partially quench-hardening the blanks in their unrestrained or free condition, and then expanding the ring blanks and clamping them circumferentially to deform the blanks below the critical temperature to the desired shape and size while the metal is still sufliciently soft, after which the quenching continues while the rings are held in restrained condition.

15. The process of manufacturing steel piston rings or the like which includes the steps of forming the blanks, heating the blanks above the critical temperature to the austenitic state, partially quench-hardening the blanks in unrestrained or free condition, and then after the temperature has fallen below the critical but while the metal is sufflciently plastic, deforming the blanks to their desired shape and completely restraining the blanks in such shape until the hard martensitic structure becomes fixed.

WALTER J. six. 

